A number of packaging forms are known. In one form, a thermoform tray is provided for retaining a product, with a flexible film forming a seal for the tray. The tray may include a peripheral flange and the film is attached to the flange. The attachment of the film to the flange may be accomplished by a variety of means, such as heat sealing, adhesives, etc. The film may be separable from the flange to gain access to the contents and the film or a portion thereof may be resealed by means of an adhesive.
It is known to use a hot-melt pressure sensitive adhesive (PSA) that is extruded between film layers of polyethylene terephthalate (PET) and polyethylene (PE) to create a resealable lidding layer. This structure requires adhesive applied as a 100% coverage coating (i.e., not pattern applied between the PET and PE layers).
U.S. Pat. No. 4,206,844 to Thukanato et al. shows a package with a cover sheet that is peelable for the package base and the resealable. The package body is formed of a laminate having a paper substrate, a polyester emulsion layer and a thermoplastic resin emulsion layer on the polyester emulsion layer. A heat seal is formed between the cover sheet and the thermoplastic resin emulsion layer to seal the package. When the cover sheet is peeled back, a portion of the thermoplastic resin layer is broken at the heat seal.
U.S. Pat. No. 4,364,989 to Moyle shows a package material for use in retaining snack foods. The package material is composed of multiple layers with an outer layer of polypropylene (PP), a low-density polyethylene (PE) laminate and an inner layer of a co-extrusion material. Emulsion layers of polyvinyl chloride (PVC) are provided between the packaging layers and are used to create a heat sealant in the formation of the package.
U.S. Pat. No. 3,454,210 to Spiegel et al. shows a multilayer package having a central, rupturable, preformed-film layer of polyethylene (PE). The rupturable film is formed adjacent a layer of pressure sensitive adhesive (PSA). A heat seal is formed to secure the rupturable film to the base layer in the sealed package.
U.S. Pat. No. 5,518,790 to Huber et al shows a multilayer package for sealing an aromatic substance. A central layer formed from a foamed polypropylene is provided between a barrier layer in a top laminate and the base layers in the package. The top layer is secured to the foamed polypropylene (PP) by an adhesive. The separation of the top layer is indicated to result from the difference in density of the top layer and the foamed PP.